JP6965996B2 - Slurry and polishing method - Google Patents

Description

The present invention relates to a slurry and a polishing method.

In recent years, in the manufacturing process of semiconductor devices, the importance of processing technology for high density and miniaturization is increasing more and more. CMP (Chemical Mechanical Polishing) technology, which is one of the processing technologies, is the formation of shallow trench isolation (shallow trench isolation, hereinafter referred to as "STI") in the manufacturing process of semiconductor devices. It is an indispensable technology for flattening pre-metal insulating materials or interlayer isolation materials, and for forming plugs or embedded metal wiring.

Examples of the most frequently used polishing liquid include silica-based polishing liquid containing silica (silicon oxide) particles such as fumed silica and colloidal silica as abrasive grains. The silica-based polishing liquid is characterized by high versatility, and a wide variety of materials can be polished regardless of the insulating material and the conductive material by appropriately selecting the abrasive grain content, pH, additives and the like.

On the other hand, there is an increasing demand for a polishing liquid containing cerium compound particles as abrasive grains as a polishing liquid mainly for insulating materials such as silicon oxide. For example, a cerium oxide-based polishing solution containing cerium oxide particles as abrasive grains can polish silicon oxide at a higher speed even with a lower abrasive grain content than a silica-based polishing solution (see, for example, Patent Documents 1 and 2 below).

Japanese Unexamined Patent Publication No. 10-106994 Japanese Unexamined Patent Publication No. 08-022970

By the way, in recent years, 3D-NAND devices in which cell portions of devices are laminated in the vertical direction have emerged. In this technology, the step of the insulating material at the time of cell formation is several times higher than that of the conventional planar type. Along with this, in order to maintain the throughput of device manufacturing, it is necessary to quickly eliminate the high step as described above in the CMP process or the like, and it is necessary to improve the polishing speed of the insulating material.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a slurry capable of improving the polishing speed of an insulating material and a polishing method using the slurry.

The slurry according to one aspect of the present invention contains abrasive grains and a liquid medium, and the abrasive grains include a first particle and a second particle in contact with the first particle. The second particle contains at least one metal compound selected from the group consisting of a metal oxide and a metal hydroxide, the metal compound contains a metal having a plurality of valences, and the plurality of the metals. The ratio of the smallest valence among the valences of is 0.10 or more in X-ray photoelectron spectroscopy.

According to the slurry according to one aspect of the present invention, it is possible to improve the polishing rate of the insulating material, and the insulating material can be polished at a high polishing rate.

The polishing method according to another aspect of the present invention includes a step of polishing the surface to be polished using the slurry. According to such a polishing method, by using the slurry, the same effect as that of the slurry can be obtained.

According to the present invention, it is possible to provide a slurry capable of improving the polishing speed of an insulating material and a polishing method using the slurry.

According to the present invention, it is possible to provide the use of a slurry for polishing a surface to be polished containing an insulating material. According to the present invention, it is possible to provide the use of a slurry in a process of flattening a surface of a substrate, which is a technique for manufacturing a semiconductor device. According to the present invention, it is possible to provide the use of a slurry in a flattening step of an STI insulating material, a premetal insulating material or an interlayer insulating material.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

<Definition>
In the present specification, the numerical range indicated by using "~" indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively. In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" may include either A or B, or both. Unless otherwise specified, the materials exemplified in the present specification may be used alone or in combination of two or more. In the present specification, the content of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. Means. The term "process" is included in this term not only in an independent process but also in the case where the desired action of the process is achieved even if it cannot be clearly distinguished from other processes.

As will be described later, the slurry according to this embodiment contains abrasive grains. Abrasive particles are also called "abrasive particles", but are referred to as "abrasive particles" in the present specification. Abrasive particles are generally solid particles, and are to be removed by the mechanical action (physical action) of the abrasive grains and the chemical action of the abrasive grains (mainly the surface of the abrasive grains) during polishing. It is believed that the object will be removed, but not limited to this. The polishing rate when the slurry according to this embodiment is used is, for example, the polishing rate obtained when the content of abrasive grains (total amount of particles) is adjusted to 0.1% by mass based on the total mass of the slurry. Can be compared based on.

As used herein, a "polishing liquid" (abrasive) is defined as a composition that comes into contact with the surface to be polished during polishing. The phrase "polishing liquid" itself does not limit the components contained in the polishing liquid.

The weight average molecular weight in the present specification can be measured, for example, by gel permeation chromatography (GPC) using a standard polystyrene calibration curve under the following conditions.
Equipment used: Hitachi L-6000 type [manufactured by Hitachi, Ltd.]
Column: Gelpack GL-R420 + Gelpack GL-R430 + Gelpack GL-R440 [Product name manufactured by Hitachi Kasei Co., Ltd., 3 in total]
Eluent: tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 1.75 mL / min
Detector: L-3300RI [manufactured by Hitachi, Ltd.]

<Slurry>
The slurry according to the present embodiment contains abrasive grains and a liquid medium as essential components. The slurry according to this embodiment can be used as, for example, a polishing liquid (CMP polishing liquid).

The abrasive grains contain composite particles containing the first particles and the second particles in contact with the first particles. The second particle contains at least one metal compound selected from the group consisting of metal oxides and metal hydroxides, and the metal compound contains a metal having a plurality of valences (valences). The ratio of the smallest valence among the plurality of valences of the metal is 0.10 or more in X-ray Photoelectron Spectroscopy (XPS).

By using the slurry according to the present embodiment, the polishing speed of the insulating material (for example, silicon oxide) can be improved. Reasons for improving the polishing rate of the insulating material in this way include, for example, the following reasons, for example, silicon oxide. However, the reason is not limited to the following.

That is, in polishing silicon oxide, the first step of bonding the metal atom in the abrasive grains and the silicon atom of silicon oxide via the oxygen atom (for example, Ce—O—Si bond when the metal atom is cerium). The silicon atom is removed from the surface to be polished by breaking the bond between the silicon atom and other oxygen atoms on the surface to be polished while maintaining the bond of metal atom-oxygen atom-silicon atom. The second step is to occur. When the abrasive grains come into contact with silicon oxide, the larger the ratio of the smallest valence among the valences of the metal in the abrasive grains, the easier it is for the first step to proceed. Therefore, the polishing of silicon oxide as a whole is performed. Easy to progress. From this point of view, when the ratio of the smallest valence among the plurality of valences of the metal contained in the abrasive grains is equal to or higher than the above-mentioned predetermined value, the first step is likely to proceed, so that silicon oxide is used. Polishing is easy to proceed as a whole. From the above, the polishing speed of silicon oxide is improved.

(Abrasive grain)
As described above, the abrasive grains of the slurry according to the present embodiment include composite particles containing the first particles and the second particles in contact with the first particles. The second particle contains at least one metal compound selected from the group consisting of a metal oxide and a metal hydroxide, and the metal compound is a metal having a plurality of valences (hereinafter, referred to as "metal M"). including. That is, the second particle contains at least one selected from the group consisting of an oxide containing a metal M and a hydroxide containing a metal M.

In the slurry according to the present embodiment, the ratio of the smallest valence among the plurality of valences of the metal M is 0.10 or more in X-ray photoelectron spectroscopy from the viewpoint of improving the polishing rate of the insulating material. The ratio of the valence is the ratio when the total amount of the metal M (all atoms) is 1, and is the ratio of the number of atoms having the target valence (unit: at%). The ratio of valences can be measured by the method described in Examples. The peak position of the X-ray photoelectron spectroscopic spectrum varies depending on the valence due to the chemical shift. On the other hand, the number of atoms in each peak is proportional to the area of the peak. Therefore, the ratio of the number of atoms of each valence can be obtained based on the shape of the spectrum. Examples of the method for adjusting the valence of the metal M include a method of subjecting the abrasive grains to an oxidation treatment or a reduction treatment. Examples of the oxidation treatment method include a method of treating abrasive grains with a reagent having an oxidizing action; a method of treating at a high temperature in air or in an oxygen atmosphere. Examples of the method of reduction treatment include a method of treating abrasive grains with a reagent having a reducing action; a method of treating at high temperature in a reducing atmosphere such as hydrogen. The metal M may have a plurality of valences. The smallest valence may be, for example, trivalent.

The ratio of the valences is preferably 0.12 or more, more preferably 0.14 or more, further preferably 0.15 or more, and particularly preferably 0.16 or more, from the viewpoint of further improving the polishing rate of the insulating material. The ratio of the valences is preferably 0.50 or less from the viewpoint of further improving the polishing rate of the insulating material.

The particle size of the second particle is preferably smaller than the particle size of the first particle. The magnitude relationship between the particle sizes of the first particles and the second particles can be determined from the SEM image of the composite particles and the like. In general, particles having a small particle size have a higher surface area per unit mass than particles having a large particle size, and therefore have higher reaction activity. On the other hand, the mechanical action (mechanical polishing force) of the particles having a small particle size is smaller than that of the particles having a large particle size. However, in the present embodiment, even when the particle size of the second particle is smaller than the particle size of the first particle, it is possible to exhibit the synergistic effect of the first particle and the second particle. Therefore, excellent reaction activity and mechanical action can be easily compatible with each other.

The lower limit of the particle size of the first particles is preferably 15 nm or more, more preferably 25 nm or more, further preferably 35 nm or more, particularly preferably 40 nm or more, and extremely preferably 50 nm or more from the viewpoint of further improving the polishing rate of the insulating material. Preferably, 80 nm or more is very preferable, and 100 nm or more is even more preferable. The upper limit of the particle size of the first particle is preferably 1000 nm or less, more preferably 800 nm or less, and more preferably 600 nm from the viewpoint of improving the dispersibility of the abrasive grains and easily suppressing scratches on the surface to be polished. The following is further preferable, 400 nm or less is particularly preferable, 300 nm or less is extremely preferable, 200 nm or less is very preferable, and 150 nm or less is even more preferable. From the above viewpoint, the particle size of the first particles is more preferably 15 to 1000 nm. The average particle size (average secondary particle size) of the first particles may be in the above range.

The lower limit of the particle size of the second particles is preferably 1 nm or more, more preferably 2 nm or more, still more preferably 3 nm or more, from the viewpoint of further improving the polishing rate of the insulating material. The upper limit of the particle size of the second particle is preferably 50 nm or less, more preferably 30 nm or less, and more preferably 25 nm from the viewpoint of improving the dispersibility of the abrasive grains and easily suppressing scratches on the surface to be polished. The following is more preferable, 20 nm or less is particularly preferable, 15 nm or less is extremely preferable, and 10 nm or less is very preferable. From the above viewpoint, the particle size of the second particle is more preferably 1 to 50 nm. The average particle size (average secondary particle size) of the second particles may be in the above range.

The average particle size (average secondary particle size) of the abrasive grains (the entire abrasive grains including composite particles and free particles) in the slurry is preferably in the following range. The lower limit of the average particle size of the abrasive grains is preferably 16 nm or more, more preferably 20 nm or more, further preferably 30 nm or more, particularly preferably 40 nm or more, and extremely preferably 50 nm or more from the viewpoint of further improving the polishing rate of the insulating material. , 100 nm or more is very preferable, 120 nm or more is even more preferable, and 140 nm or more is even more preferable. The upper limit of the average particle size of the abrasive grains is preferably 1050 nm or less, more preferably 1000 nm or less, and more preferably 800 nm or less from the viewpoint of improving the dispersibility of the abrasive grains and easily suppressing scratches on the surface to be polished. Is particularly preferable, 600 nm or less is particularly preferable, 500 nm or less is extremely preferable, 400 nm or less is very preferable, 300 nm or less is even more preferable, 200 nm or less is further preferable, 160 nm or less is particularly preferable, and 155 nm or less is extremely preferable. From the above viewpoint, the average particle size of the abrasive grains is more preferably 16 to 150 nm.

The average particle size is measured using, for example, a light diffraction / scattering type particle size distribution meter (for example, manufactured by Beckman Coulter Co., Ltd., trade name: N5, or manufactured by Microtrack Bell Co., Ltd., trade name: Microtrack MT3300EXII). can do.

The zeta potential of the abrasive grains (the zeta potential of the entire abrasive grains) in the slurry is preferably in the following range. The zeta potential of the abrasive grains is preferably +10 mV or more, more preferably +20 mV or more, further preferably +25 mV or more, particularly preferably +30 mV or more, extremely preferably +40 mV or more, and +50 mV or more from the viewpoint of further improving the polishing speed of the insulating material. Is very preferable. The upper limit of the zeta potential of the abrasive grains is not particularly limited, and is, for example, +200 mV or less.

The first particle can have a negative zeta potential. The second particle can have a positive zeta potential.

The zeta potential represents the surface potential of a particle. The zeta potential can be measured using, for example, a dynamic light scattering type zeta potential measuring device (for example, manufactured by Beckman Coulter, Inc., trade name: DelsaNano C). The zeta potential of the particles can be adjusted with additives. For example, by contacting a particle containing a cerium oxide with a monocarboxylic acid (for example, acetic acid), particles having a positive zeta potential can be obtained. Further, by contacting the particles containing the cerium oxide with ammonium dihydrogen phosphate, a material having a carboxyl group (for example, polyacrylic acid), or the like, particles having a negative zeta potential can be obtained.

The first particles are silicon (Si), vanadium (V), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Si), from the viewpoint of further improving the polishing speed of the insulating material. At least one metal selected from the group consisting of Cu), silver (Ag), indium (In), tin (Sn), rare earth element (rare earth metal element), tungsten (W), and bismuth (Bi) (hereinafter referred to as "Bi"). It is preferable to include (referred to as "metal m"). The metal m preferably contains at least one selected from the group consisting of scandium (Sc) and lanthanoids as a rare earth element from the viewpoint of further improving the polishing rate of the insulating material. The metal m is selected from the group consisting of cerium (Ce), praseodymium (Pr), europium (Eu), terbium (Tb), and ytterbium (Yb) as lanthanoids from the viewpoint of further improving the polishing speed of the insulating material. It is preferable to include at least one of these. From the viewpoint of further improving the polishing rate of the insulating material, the metal m preferably contains a rare earth element, more preferably contains a lanthanoid, and further preferably contains cerium.

The first particle may contain an organic compound and may contain a polymer compound (polymer). Examples of the polymer compound include polystyrene, polyphenylene sulfide, polyamideimide, epoxy resin, polyvinylidene fluoride, polyethylene terephthalate, polybutylene terephthalate, polyester, polyether sulfone, polylactic acid, ethyl cellulose resin, acrylic resin and the like.

The metal M of the second particle preferably contains a rare earth metal, more preferably contains a lanthanoid, and further preferably contains cerium from the viewpoint of further improving the polishing rate of the insulating material. As the lanthanoid, at least one selected from the group consisting of cerium, praseodymium, europium, terbium, ytterbium, and lutetium can be used.

The second particle preferably contains a metal hydroxide, and more preferably contains a hydroxide containing cerium (cerium hydroxide) from the viewpoint of further improving the polishing rate of the insulating material. Abrasive grains containing cerium hydroxide have higher reactivity (chemical action) with an insulating material (for example, silicon oxide) due to the action of hydroxyl groups than particles made of silica, cerium oxide, etc. It can be polished at a higher polishing speed. The cerium hydroxide is, for example, a compound containing a cerium ion and at least one hydroxide ion (OH ^−). Cerium hydroxide anions other than hydroxide ion (e.g., nitrate ion NO ₃ ^- and sulfate ions _SO ^{4 2-)} may contain. For example, cerium hydroxide, anion bound to cerium ions (e.g., nitrate ion NO ₃ ^- and sulfate ions SO 4 ^_2-) may contain.

The cerium hydroxide can be produced by reacting a cerium salt with an alkaline source (base). The cerium hydroxide can be prepared by mixing a cerium salt and an alkaline solution (for example, an alkaline aqueous solution). The cerium hydroxide can be obtained by mixing a cerium salt solution (for example, a cerium salt aqueous solution) and an alkaline solution. Examples of the cerium salt include Ce (NO ₃ ) ₄ , Ce (SO ₄ ) ₂ , Ce (NH ₄ ) ₂ (NO ₃ ) ₆ , Ce (NH ₄ ) ₄ (SO ₄ ) _{4, and the} like.

Ce (OH) _a X _b consisting of cerium ions, 1 to 3 hydroxide ions (OH ⁻ ) and 1 to 3 anions (X ^{c −), depending on the production conditions of cerium hydroxide.} It is considered that particles containing (in the formula, a + b × c = 4) are generated (note that such particles are also cerium hydroxides). In Ce (OH) _a X _b , electron-withdrawing anions (X ^c- ) act to improve the reactivity of hydroxide ions, and the abundance of _{Ce (OH) a} X _{b increases.} It is considered that the polishing speed is improved accordingly. The anion ^{(X c-),} for example, NO ₃ ^- and _SO ^{4 2-and} the like. It is considered that the particles containing cerium hydroxide may contain _{not only Ce (OH) a} X _b but also Ce (OH) ₄ , CeO _{2, and the} like.

The fact that the particles containing cerium hydroxide contain Ce (OH) _a X _b means that the particles are thoroughly washed with pure water, and then the FT-IR ATR method (Fourier transform InfraRed Spectrometer Attenuated Total Reflection method, Fourier transform infrared) is used. It can be confirmed by a method of detecting a peak corresponding to ^{an anion (Xc-} ) by a spectrophotometer total reflection measurement method). ^{The presence of anions (Xc-} ) can also be confirmed by X-ray photoelectron spectroscopy.

In the slurry abrasive grains according to the present embodiment, the particle size of the second particles is smaller than the particle size of the first particles from the viewpoint of further improving the polishing speed of the insulating material, and the first particles are cerium oxide. It is preferable that the second particle contains at least one cerium compound selected from the group consisting of cerium oxide and cerium hydroxide. Reasons for improving the polishing speed of the insulating material in this way include, for example, the following reasons. However, the reason is not limited to the following.

That is, the first particle containing cerium oxide and having a particle size larger than that of the second particle has a stronger mechanical action (mechanical property) on the insulating material than the second particle. On the other hand, the second particle, which contains a cerium compound and has a particle size smaller than that of the first particle, has a smaller mechanical action on the insulating material than the first particle, but has a specific surface area of the entire particle. Since (surface area per unit mass) is large, it has a strong chemical action (chemical property) on the insulating material. As described above, the synergistic effect of improving the polishing speed can be easily obtained by using the first particle having a strong mechanical action and the second particle having a strong chemical action in combination.

The first particle and the composite particle containing the second particle are brought into contact with the first particle and the second particle by using a homogenizer, a nanomizer, a ball mill, a bead mill, an ultrasonic processing machine or the like, and charge opposite to each other. It can be obtained by bringing the first particle having the above into contact with the second particle, bringing the first particle into contact with the second particle in a state where the content of the particle is small, and the like.

The lower limit of the content of cerium oxide in the first particles is based on the whole of the first particles (the whole of the first particles contained in the slurry; the same applies hereinafter) from the viewpoint of further improving the polishing rate of the insulating material. As a result, 50% by mass or more is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and 95% by mass or more is particularly preferable. The first particle may be in a mode substantially composed of cerium oxide (a mode in which 100% by mass of the first particle is substantially cerium oxide).

The lower limit of the content of the cerium compound in the second particles is based on the whole of the second particles (the whole of the second particles contained in the slurry; the same applies hereinafter) from the viewpoint of further improving the polishing rate of the insulating material. , 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and particularly preferably 95% by mass or more. The second particle may be in a mode substantially composed of a cerium compound (a mode in which 100% by mass of the second particle is substantially a cerium compound).

The content of the second particle can be estimated from the absorbance value of the following formula obtained by the spectrophotometer when light of a specific wavelength is transmitted through the slurry. That is, when the particles absorb light of a specific wavelength, the light transmittance of the region containing the particles decreases. The light transmittance is reduced not only by absorption by the particles but also by scattering, but in the second particle, the influence of scattering is small. Therefore, in the present embodiment, the content of the second particle can be estimated from the value of the absorbance calculated by the following formula.
Absorbance = -LOG ₁₀ (light transmittance [%] / 100)

The lower limit of the content of the first particles in the abrasive grains is 50% by mass or more based on the entire abrasive grains (the entire abrasive grains contained in the slurry; the same applies hereinafter) from the viewpoint of further improving the polishing speed of the insulating material. It is more preferably more than 50% by mass, further preferably 60% by mass or more, particularly preferably 70% by mass or more, extremely preferably 75% by mass or more, very preferably 80% by mass or more, and 85% by mass or more. Even more preferably, 90% by mass or more is further preferable. The upper limit of the content of the first particles in the abrasive grains is preferably 95% by mass or less, more preferably 93% by mass or less, and 91% by mass, based on the entire abrasive grains, from the viewpoint of further improving the polishing rate of the insulating material. % Or less is more preferable. From the above viewpoint, the content of the first particles in the abrasive grains is more preferably 50 to 95% by mass with respect to the entire abrasive grains.

The lower limit of the content of the second particles in the abrasive grains is preferably 5% by mass or more based on the entire abrasive grains (the entire abrasive grains contained in the slurry) from the viewpoint of further improving the polishing speed of the insulating material. It is more preferably 9% by mass or more, and further preferably 9% by mass or more. The upper limit of the content of the second particles in the abrasive grains is preferably 50% by mass or less, more preferably less than 50% by mass, and 40% by mass, based on the entire abrasive grains, from the viewpoint of further improving the polishing rate of the insulating material. % Or less is more preferable, 30% by mass or less is particularly preferable, 20% by mass or less is extremely preferable, and 10% by mass or less is very preferable. From the above viewpoint, the content of the second particles in the abrasive grains is more preferably 5 to 50% by mass with respect to the entire abrasive grains.

The lower limit of the content of cerium oxide in the abrasive grains is preferably 50% by mass or more, preferably 50% by mass or more, based on the entire abrasive grains (the entire abrasive grains contained in the slurry) from the viewpoint of further improving the polishing speed of the insulating material. % Is more preferable, 60% by mass or more is further preferable, 70% by mass or more is particularly preferable, 75% by mass or more is extremely preferable, 80% by mass or more is very preferable, and 85% by mass or more is even more preferable. 90% by mass or more is more preferable. The upper limit of the content of cerium oxide in the abrasive grains is preferably 95% by mass or less, more preferably 93% by mass or less, and 91% by mass, based on the entire abrasive grains, from the viewpoint of further improving the polishing rate of the insulating material. The following is more preferable. From the above viewpoint, the content of the cerium oxide in the abrasive grains is more preferably 50 to 95% by mass with respect to the entire abrasive grains.

The lower limit of the content of cerium hydroxide in the abrasive grains is preferably 5% by mass or more based on the entire abrasive grains (the entire abrasive grains contained in the slurry) from the viewpoint of further improving the polishing rate of the insulating material. More preferably, it is 9% by mass or more, and further preferably 9% by mass or more. The upper limit of the content of cerium hydroxide in the abrasive grains is preferably 50% by mass or less, more preferably less than 50% by mass, and 40% by mass, based on the entire abrasive grains, from the viewpoint of further improving the polishing rate of the insulating material. % Or less is more preferable, 30% by mass or less is particularly preferable, 20% by mass or less is extremely preferable, and 10% by mass or less is very preferable. From the above viewpoint, the content of cerium hydroxide in the abrasive grains is more preferably 5 to 50% by mass based on the entire abrasive grains.

The lower limit of the content of the first particles is preferably 50% by mass or more, preferably 50% by mass, based on the total amount of the first particles and the second particles from the viewpoint of further improving the polishing rate of the insulating material. More preferably, it is more preferably 60% by mass or more, particularly preferably 70% by mass or more, extremely preferably 75% by mass or more, very preferably 80% by mass or more, even more preferably 85% by mass or more, and 90% by mass. % Or more is more preferable. The upper limit of the content of the first particles is preferably 95% by mass or less, preferably 93% by mass or less, based on the total amount of the first particles and the second particles, from the viewpoint of further improving the polishing rate of the insulating material. Is more preferable, and 91% by mass or less is further preferable. From the above viewpoint, the content of the first particles is more preferably 50 to 95% by mass based on the total amount of the first particles and the second particles.

The lower limit of the content of the second particles is preferably 5% by mass or more, preferably 7% by mass or more, based on the total amount of the first particles and the second particles from the viewpoint of further improving the polishing rate of the insulating material. Is more preferable, and 9% by mass or more is further preferable. The upper limit of the content of the second particles is preferably 50% by mass or less, preferably less than 50% by mass, based on the total amount of the first particles and the second particles, from the viewpoint of further improving the polishing rate of the insulating material. Is more preferable, 40% by mass or less is further preferable, 30% by mass or less is particularly preferable, 20% by mass or less is extremely preferable, and 10% by mass or less is very preferable. From the above viewpoint, the content of the second particle is more preferably 5 to 50% by mass based on the total amount of the first particle and the second particle.

The lower limit of the content of the first particles in the slurry is preferably 0.005% by mass or more, more preferably 0.008% by mass or more, based on the total mass of the slurry, from the viewpoint of further improving the polishing rate of the insulating material. Preferably, 0.01% by mass or more is further preferable, 0.05% by mass or more is particularly preferable, 0.07% by mass or more is extremely preferable, and 0.08% by mass or more is very preferable. The upper limit of the content of the first particles in the slurry is 5% by mass or less based on the total mass of the slurry from the viewpoint of further improving the polishing speed of the insulating material and increasing the storage stability of the slurry. Preferably, 3% by mass or less is more preferable, 1% by mass or less is further preferable, 0.5% by mass or less is particularly preferable, 0.3% by mass or less is extremely preferable, 0.1% by mass or less is very preferable, and 0. .09% by mass or less is even more preferable, and 0.085% by mass or less is even more preferable. From the above viewpoint, the content of the first particles in the slurry is more preferably 0.005 to 5% by mass based on the total mass of the slurry.

The lower limit of the content of the second particle in the slurry is based on the total mass of the slurry from the viewpoint of further improving the chemical interaction between the abrasive grains and the surface to be polished and further improving the polishing speed of the insulating material. , 0.005% by mass or more, more preferably 0.008% by mass or more, further preferably 0.01% by mass or more, particularly preferably 0.012% by mass or more, and extremely preferably 0.015% by mass or more. 0.016% by mass or more is very preferable. The upper limit of the content of the second particle in the slurry makes it easy to avoid agglomeration of the abrasive grains, and further improves the chemical interaction between the abrasive grains and the surface to be polished, so that the characteristics of the abrasive grains are effective. From the viewpoint of easy utilization, 5% by mass or less is preferable, 3% by mass or less is more preferable, 1% by mass or less is further preferable, 0.5% by mass or less is particularly preferable, and 0. 1% by mass or less is extremely preferable, 0.05% by mass or less is very preferable, 0.04% by mass or less is further preferable, 0.035% by mass or less is further preferable, and 0.03% by mass or less is further preferable. 0.02% by mass or less is particularly preferable, and 0.018% by mass or less is extremely preferable. From the above viewpoint, the content of the second particles in the slurry is more preferably 0.005 to 5% by mass based on the total mass of the slurry.

The lower limit of the content of cerium oxide in the slurry is preferably 0.005% by mass or more, more preferably 0.008% by mass or more, based on the total mass of the slurry, from the viewpoint of further improving the polishing rate of the insulating material. , 0.01% by mass or more is further preferable, 0.05% by mass or more is particularly preferable, 0.07% by mass or more is extremely preferable, and 0.08% by mass or more is very preferable. The upper limit of the content of cerium oxide in the slurry is preferably 5% by mass or less based on the total mass of the slurry from the viewpoint of further improving the polishing rate of the insulating material and increasing the storage stability of the slurry. 3, 3% by mass or less is more preferable, 1% by mass or less is further preferable, 0.5% by mass or less is particularly preferable, 0.3% by mass or less is extremely preferable, 0.1% by mass or less is very preferable, and 0. 09% by mass or less is even more preferable, and 0.085% by mass or less is even more preferable. From the above viewpoint, the content of cerium oxide in the slurry is more preferably 0.005 to 5% by mass based on the total mass of the slurry.

The lower limit of the content of cerium hydroxide in the slurry is based on the total mass of the slurry from the viewpoint of further improving the chemical interaction between the abrasive grains and the surface to be polished and further improving the polishing speed of the insulating material. , 0.005% by mass or more, more preferably 0.008% by mass or more, further preferably 0.01% by mass or more, particularly preferably 0.012% by mass or more, and extremely preferably 0.015% by mass or more. 0.016% by mass or more is very preferable. The upper limit of the content of cerium hydroxide in the slurry makes it easy to avoid agglomeration of abrasive grains, and further improves the chemical interaction between the abrasive grains and the surface to be polished, which makes the characteristics of the abrasive grains effective. From the viewpoint of easy utilization, 5% by mass or less is preferable, 3% by mass or less is more preferable, 1% by mass or less is further preferable, 0.5% by mass or less is particularly preferable, and 0. 1% by mass or less is extremely preferable, 0.05% by mass or less is very preferable, 0.04% by mass or less is further preferable, 0.035% by mass or less is further preferable, and 0.03% by mass or less is further preferable. 0.02% by mass or less is particularly preferable, and 0.018% by mass or less is extremely preferable. From the above viewpoint, the content of cerium hydroxide in the slurry is more preferably 0.005 to 5% by mass based on the total mass of the slurry.

The lower limit of the abrasive grain content in the slurry is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the total mass of the slurry, from the viewpoint of further improving the polishing rate of the insulating material. 0.08% by mass or more is more preferable, and 0.1% by mass or more is particularly preferable. The upper limit of the content of abrasive grains in the slurry is preferably 10% by mass or less, more preferably 5% by mass or less, and 1% by mass or less, based on the total mass of the slurry, from the viewpoint of increasing the storage stability of the slurry. More preferably, 0.5% by mass or less is particularly preferable, 0.1% by mass or less is extremely preferable, 0.2% by mass or less is very preferable, 0.15% by mass or less is even more preferable, and 0.135% by mass or less. The following is more preferable, and 0.13% by mass or less is particularly preferable. From the above viewpoint, the content of abrasive grains in the slurry is more preferably 0.01 to 10% by mass based on the total mass of the slurry.

The slurry according to the present embodiment may contain particles other than the first particles and composite particles containing the second particles. Examples of such other particles include the first particle that is not in contact with the second particle; the second particle that is not in contact with the first particle; silica, alumina, zirconia, yttria. A third particle (a particle not containing the first particle and the second particle) composed of the above can be mentioned.

(Liquid medium)
The liquid medium is not particularly limited, but water such as deionized water and ultrapure water is preferable. The content of the liquid medium may be the balance of the slurry excluding the content of other constituent components, and is not particularly limited.

(Arbitrary ingredient)
The slurry according to the present embodiment may further contain any additive. Optional additives include materials having a carboxyl group (excluding polyoxyalkylene compounds or compounds corresponding to water-soluble polymers), polyoxyalkylene compounds, water-soluble polymers, oxidizing agents (for example, hydrogen peroxide), and dispersions. Examples thereof include agents (for example, phosphoric acid-based inorganic salts). Each of the additives can be used alone or in combination of two or more.

Materials having a carboxyl group include monocarboxylic acids such as acetic acid, propionic acid, butyric acid, and valeric acid; hydroxy acids such as lactic acid, malic acid, and citric acid; and dicarboxylic acids such as malonic acid, succinic acid, fumaric acid, and maleic acid. Polycarboxylic acids such as polyacrylic acid and polymaleic acid; amino acids such as arginine, histidine, and lysine.

Examples of the polyoxyalkylene compound include polyalkylene glycols and polyoxyalkylene derivatives.

Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like. As the polyalkylene glycol, at least one selected from the group consisting of polyethylene glycol and polypropylene glycol is preferable, and polyethylene glycol is more preferable.

The polyoxyalkylene derivative is, for example, a compound in which a functional group or a substituent is introduced into a polyalkylene glycol, or a compound in which a polyalkylene oxide is added to an organic compound. Examples of the functional group or substituent include an alkyl ether group, an alkyl phenyl ether group, a phenyl ether group, a styrene phenyl ether group, a glyceryl ether group, an alkyl amine group, a fatty acid ester group, and a glycol ester group. .. Examples of the polyoxyalkylene derivative include polyoxyethylene alkyl ether, polyoxyethylene bisphenol ether (for example, manufactured by Nippon Emulsifier Co., Ltd., BA glycol series), and polyoxyethylene styrene phenyl ether (for example, manufactured by Kao Co., Ltd., Emargen). Series), polyoxyethylene alkyl phenyl ether (for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neugen EA series), polyoxyalkylene polyglyceryl ether (for example, manufactured by Sakamoto Pharmaceutical Co., Ltd., SC-E series and SC-P series). , Polyoxyethylene sorbitan fatty acid ester (for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Sorgen TW series), polyoxyethylene fatty acid ester (for example, manufactured by Kao Co., Ltd., Emanon series), polyoxyethylene alkylamine (for example, No. 1) (Amyradin D) manufactured by Ichiko Pharmaceutical Co., Ltd., and other compounds to which polyalkylene oxide is added (for example, Surfinol 465 manufactured by Nisshin Chemical Industry Co., Ltd. and TMP series manufactured by Nippon Emulsifier Co., Ltd.) are mentioned. Be done.

The "water-soluble polymer" is defined as a polymer that dissolves 0.1 g or more in 100 g of water. The polymer corresponding to the polyoxyalkylene compound shall not be included in the "water-soluble polymer". The water-soluble polymer is not particularly limited, and acrylic polymers such as polyacrylamide and polydimethylacrylamide; polysaccharides such as carboxymethyl cellulose, agar, curdran, dextrin, cyclodextrin, and pullulan; polyvinyl alcohol, polyvinylpyrrolidone, and poly. Vinyl-based polymers such as achlorin; glycerin-based polymers such as polyglycerin and polyglycerin derivatives; polyethylene glycol and the like can be mentioned.

(Characteristics of slurry)
The lower limit of the pH of the slurry according to the present embodiment is preferably 2.0 or more, more preferably 2.5 or more, further preferably 2.8 or more, and 3.0 or more, from the viewpoint of further improving the polishing rate of the insulating material. The above is particularly preferable, 3.2 or more is extremely preferable, 3.5 or more is very preferable, 4.0 or more is even more preferable, and 4.1 or more is further preferable. The upper limit of pH is preferably 7.0 or less, more preferably 6.5 or less, further preferably 6.0 or less, particularly preferably 5.0 or less, from the viewpoint of further improving the storage stability of the slurry. 8 or less is extremely preferable, 4.7 or less is very preferable, 4.6 or less is even more preferable, 4.5 or less is further preferable, and 4.4 or less is particularly preferable. From the above viewpoint, the pH is more preferably 2.0 to 7.0. The pH of the slurry is defined as the pH at a liquid temperature of 25 ° C.

The pH of the slurry can be adjusted by an acid component such as an inorganic acid or an organic acid; an alkaline component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), imidazole, or alkanolamine. In addition, a buffer may be added to stabilize the pH. Moreover, you may add a buffering agent as a buffering liquid (a liquid containing a buffering agent). Examples of such a buffer solution include an acetate buffer solution and a phthalate buffer solution.

The pH of the slurry according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by DKK-TOA CORPORATION). Specifically, for example, after calibrating the pH meter at two points using a phthalate pH buffer solution (pH: 4.01) and a neutral phosphate pH buffer solution (pH: 6.86) as standard buffer solutions. , Put the electrode of the pH meter in the slurry and measure the value after it stabilizes after 2 minutes or more. The temperature of both the standard buffer solution and the slurry is 25 ° C.

When the slurry according to the present embodiment is used as a CMP polishing liquid, the constituent components of the polishing liquid may be stored as a one-component polishing liquid, and a slurry (first liquid) containing abrasive grains and a liquid medium and an additive A multi-component type (for example, a two-component type) in which the constituent components of the polishing liquid are divided into a slurry and an additive liquid so as to be obtained by mixing the additive liquid (second liquid) containing the liquid medium and the polishing liquid. It may be stored as a polishing liquid set. The additive liquid may contain, for example, an oxidizing agent. The constituent components of the polishing liquid may be stored as a polishing liquid set divided into three or more liquids.

In the polishing liquid set, a slurry and an additive liquid are mixed immediately before polishing or at the time of polishing to prepare a polishing liquid. Further, the one-component polishing liquid may be stored as a storage liquid for a polishing liquid in which the content of the liquid medium is reduced, and may be diluted with a liquid medium at the time of polishing and used. The multi-liquid type polishing liquid set may be stored as a storage liquid for slurry and a storage liquid for additive liquid in which the content of the liquid medium is reduced, and may be diluted with a liquid medium at the time of polishing.

<Polishing method>
The polishing method according to the present embodiment (polishing method of the substrate, etc.) includes a polishing step of polishing the surface to be polished (surface to be polished of the substrate, etc.) using the slurry. The slurry in the polishing step may be a polishing liquid obtained by mixing the slurry and the additive liquid in the polishing liquid set.

In the polishing step, for example, the slurry is supplied between the material to be polished and the polishing pad in a state where the material to be polished of the substrate having the material to be polished is pressed against the polishing pad (polishing cloth) of the polishing platen. The surface to be polished of the material to be polished is polished by relatively moving the substrate and the polishing platen. In the polishing step, for example, at least a part of the material to be polished is removed by polishing.

Examples of the substrate to be polished include a substrate to be polished. Examples of the substrate to be polished include a substrate in which a material to be polished is formed on a substrate (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed) related to manufacturing a semiconductor element. Examples of the material to be polished include an insulating material such as silicon oxide. The material to be polished may be a single material or a plurality of materials. When a plurality of materials are exposed on the surface to be polished, they can be regarded as the materials to be polished. The material to be polished may be in the form of a film (film to be polished), or may be an insulating film such as a silicon oxide film.

By polishing the material to be polished (for example, an insulating material such as silicon oxide) formed on such a substrate with the slurry and removing the excess portion, the unevenness of the surface of the material to be polished is eliminated and the surface to be polished is covered. A smooth surface can be obtained over the entire surface of the polishing material.

In the polishing method according to the present embodiment, as the polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate having a surface to be polished and a polishing surface plate to which a polishing pad can be attached can be used. A motor or the like whose rotation speed can be changed is attached to each of the holder and the polishing surface plate. As the polishing device, for example, a polishing device manufactured by Ebara Corporation: F-REX300 or a polishing device manufactured by Applied Materials Co., Ltd .: MIRRA can be used.

As the polishing pad, a general non-woven fabric, foam, non-foam or the like can be used. As the material of the polishing pad, polyurethane, acrylic resin, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trade name)) And aramid), polyimide, polyimideamide, polysiloxane copolymer, oxylan compound, phenol resin, polystyrene, polycarbonate, epoxy resin and other resins can be used. As the material of the polishing pad, at least one selected from the group consisting of foamed polyurethane and non-foamed polyurethane is preferable from the viewpoint of further excellent polishing speed and flatness. It is preferable that the polishing pad is grooved so that slurry can be accumulated.

Although there is no limit to the polishing conditions, the upper limit of the rotational speed of the polishing platen is preferably ^200min -1 ^(min -1 = rpm) or less so as not fly out is base, the upper limit of the polishing pressure (working load) applied to the substrate Is preferably 100 kPa or less from the viewpoint of easily suppressing the occurrence of polishing scratches. During polishing, it is preferable to continuously supply the slurry to the polishing pad with a pump or the like. There is no limit to the amount of this supply, but it is preferable that the surface of the polishing pad is always covered with slurry.

This embodiment is preferably used for polishing the surface to be polished containing silicon oxide. According to this embodiment, it is possible to provide the use of a slurry for polishing a surface to be polished containing silicon oxide. This embodiment can be suitably used for forming STI and high-speed polishing of interlayer insulating materials. The lower limit of the polishing rate of the insulating material (for example, silicon oxide) is preferably 850 nm / min or more, more preferably 900 nm / min or more, and further preferably 1000 nm / min or more.

The present embodiment can also be used for polishing a premetal insulating material. Examples of the premetal insulating material include silicon oxide, phosphorus-silicate glass, boron-phosphorus-silicate glass, silicon oxyfluorolide, and amorphous carbon fluoride.

This embodiment can be applied to materials other than insulating materials such as silicon oxide. Examples of such materials include high dielectric constant materials such as Hf-based, Ti-based, and Ta-based oxides; semiconductor materials such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; GeSbTe and the like. Phase change material; Inorganic conductive material such as ITO; Polyimide-based, polybenzoxazole-based, acrylic-based, epoxy-based, phenol-based and other polymer resin materials and the like can be mentioned.

This embodiment can be applied not only to a film-like polishing target but also to various substrates composed of glass, silicon, SiC, SiCe, Ge, GaN, GaP, GaAs, sapphire, plastic and the like.

In this embodiment, not only the manufacture of semiconductor elements, but also image display devices such as TFTs and organic ELs; optical components such as photomasks, lenses, prisms, optical fibers, and single crystal scintillators; optical elements such as optical switching elements and optical waveguides. Light emitting elements such as solid-state lasers and blue laser LEDs; can be used in the manufacture of magnetic storage devices such as magnetic disks and magnetic heads.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

<Preparation of cerium oxide slurry>
Particles containing cerium oxide (first particles; hereinafter referred to as "cerium oxide particles") and trade name: ammonium dihydrogen phosphate (molecular weight: 97.99) manufactured by Wako Pure Chemical Industries, Ltd. are mixed. Then, a cerium oxide slurry (pH: 7) containing 5.0% by mass (solid content) of cerium oxide particles was prepared. The blending amount of ammonium dihydrogen phosphate was adjusted to 1% by mass based on the total amount of cerium oxide particles.

Trade name manufactured by Microtrac Bell Co., Ltd .: An appropriate amount of cerium oxide slurry was put into Microtrac MT3300EXII, and the average particle size of the cerium oxide particles was measured. The displayed average particle size value was obtained as the average particle size (average secondary particle size). The average particle size of the cerium oxide particles in the cerium oxide slurry was 145 nm.

A suitable amount of cerium oxide slurry was put into DelsaNano C, a trade name manufactured by Beckman Coulter Co., Ltd., and the measurement was carried out twice at 25 ° C. The average value of the displayed zeta potentials was obtained as the zeta potentials. The zeta potential of the cerium oxide particles in the cerium oxide slurry was -55 mV.

<Preparation of cerium hydroxide slurry>
(Synthesis of cerium hydroxide)
480g of _{Ce (NH 4) 2 (NO} 3) 6 50 % by weight aqueous solution (Nihon Kagaku Sangyo Co., Ltd., trade name: CAN 50 solution) to obtain a solution by mixing with pure water 7450G. Then, while stirring this solution, 750 g of an imidazole aqueous solution (10 mass% aqueous solution, 1.47 mol / L) was added dropwise at a mixing rate of 5 mL / min to obtain a precipitate containing cerium hydroxide. The synthesis of cerium hydroxide was carried out at a temperature of 20 ° C. and a stirring speed of 500 min- ^1. Stirring was performed using a 3-blade pitch paddle having a total blade length of 5 cm.

The obtained precipitate (precipitate containing cerium hydroxide) was centrifuged (4000 ^{min -1} , 5 minutes), and then the liquid phase was removed by decantation to perform solid-liquid separation. After mixing 10 g of the particles obtained by solid-liquid separation and 990 g of water, the particles are dispersed in water using an ultrasonic washing machine, and the particles containing cerium hydroxide (second particles; hereinafter, A cerium hydroxide slurry (particle content: 1.0% by mass) containing (referred to as "cerium hydroxide particles") was prepared.

(Measurement of average particle size)
When the average particle size (average secondary particle size) of the cerium hydroxide particles in the cerium hydroxide slurry was measured using Beckman Coulter Co., Ltd., trade name: N5, it was 10 nm. The measurement method is as follows. First, about 1 mL of a measurement sample (cerium hydroxide slurry, aqueous dispersion) containing 1.0% by mass of cerium hydroxide particles was placed in a 1 cm square cell, and then the cell was placed in N5. The refractive index of the measurement sample information of the software of N5 was set to 1.333 and the viscosity was set to 0.887 mPa · s, the measurement was performed at 25 ° C., and the value displayed as Unimodal Size Mean was read.

(Measurement of zeta potential)
A suitable amount of cerium hydroxide slurry was put into DelsaNano C, a trade name manufactured by Beckman Coulter Co., Ltd., and the measurement was carried out twice at 25 ° C. The average value of the displayed zeta potentials was obtained as the zeta potentials. The zeta potential of the cerium hydroxide particles in the cerium hydroxide slurry was +50 mV.

(Structural analysis of cerium hydroxide particles)
An appropriate amount of cerium hydroxide slurry was collected, vacuum dried to isolate cerium hydroxide particles, and then sufficiently washed with pure water to obtain a sample. The obtained sample was subjected to measurement by FT-IR ATR method, hydroxide ions ^- in addition to the peak based on the nitrate ion (OH) (NO ₃ ^-) peak based on was observed. Further, for the same sample, it was subjected to XPS (N-XPS) measurement for nitrogen, a peak based on NH ₄ ⁺ is not observed, a peak based on nitrate ions was observed. From these results, it was confirmed that the cerium hydroxide particles contained at least a part of the particles having nitrate ions bonded to the cerium element. Further, since particles having hydroxide ions bonded to the cerium element are contained in at least a part of the cerium hydroxide particles, it was confirmed that the cerium hydroxide particles contain the cerium hydroxide. From these results, it was confirmed that the hydroxide of cerium contains hydroxide ions bonded to the element of cerium.

<Preparation of slurry>
(Example 1)
While stirring at a rotation speed of 300 rpm using a two-blade stirring blade, 25 g of the cerium hydroxide slurry and 1935 g of ion-exchanged water were mixed to obtain a mixed solution. Subsequently, 40 g of the cerium oxide slurry is mixed with the mixed solution while stirring the mixed solution, and then ultrasonic waves are irradiated using an ultrasonic cleaner (device name: US-105) manufactured by SND Co., Ltd. It was stirred while stirring. As a result, a test slurry containing composite particles containing cerium oxide particles and cerium hydroxide particles in contact with the cerium oxide particles (content of cerium oxide particles: 0.1% by mass, cerium). Content of hydroxide particles: 0.0125% by mass) was prepared.

(Example 2)
While stirring at a rotation speed of 300 rpm using a two-bladed stirring blade, 30 g of the cerium hydroxide slurry and 1930 g of ion-exchanged water were mixed to obtain a mixed solution. Subsequently, 40 g of the cerium oxide slurry is mixed with the mixed solution while stirring the mixed solution, and then ultrasonic waves are irradiated using an ultrasonic cleaner (device name: US-105) manufactured by SND Co., Ltd. It was stirred while stirring. As a result, in addition to the composite particles containing the cerium oxide particles and the cerium hydroxide particles in contact with the cerium oxide particles, the cerium hydroxide particles (free particles) not in contact with the cerium oxide particles. A test slurry (content of cerium oxide particles: 0.1% by mass, content of cerium hydroxide particles: 0.015% by mass) containing the above was prepared.

(Example 3)
While stirring at a rotation speed of 300 rpm using a two-bladed stirring blade, 35 g of the cerium hydroxide slurry and 1925 g of ion-exchanged water were mixed to obtain a mixed solution. Subsequently, 40 g of the cerium oxide slurry is mixed with the mixed solution while stirring the mixed solution, and then ultrasonic waves are irradiated using an ultrasonic cleaner (device name: US-105) manufactured by SND Co., Ltd. It was stirred while stirring. As a result, in addition to the composite particles containing the cerium oxide particles and the cerium hydroxide particles in contact with the cerium oxide particles, the cerium hydroxide particles (free particles) not in contact with the cerium oxide particles. A test slurry (content of cerium oxide particles: 0.1% by mass, content of cerium hydroxide particles: 0.0175% by mass) containing the above was prepared.

(Example 4)
While stirring at a rotation speed of 300 rpm using a two-blade stirring blade, 40 g of the cerium hydroxide slurry and 1920 g of ion-exchanged water were mixed to obtain a mixed solution. Subsequently, 40 g of the cerium oxide slurry is mixed with the mixed solution while stirring the mixed solution, and then ultrasonic waves are irradiated using an ultrasonic cleaner (device name: US-105) manufactured by SND Co., Ltd. It was stirred while stirring. As a result, in addition to the composite particles containing the cerium oxide particles and the cerium hydroxide particles in contact with the cerium oxide particles, the cerium hydroxide particles (free particles) not in contact with the cerium oxide particles. A test slurry (content of cerium oxide particles: 0.1% by mass, content of cerium hydroxide particles: 0.02% by mass) containing the above was prepared.

(Comparative Example 1)
After mixing 40 g of the cerium oxide slurry and 1960 g of ion-exchanged water while stirring at a rotation speed of 300 rpm using a two-blade stirring blade, an ultrasonic cleaner manufactured by SND Co., Ltd. (device name: US-105) ) Was used to stir while irradiating ultrasonic waves. As a result, a test slurry containing cerium oxide particles (content of cerium oxide particles: 0.1% by mass) was prepared.

(Comparative Example 2)
After mixing 200 g of the cerium hydroxide slurry and 1800 g of ion-exchanged water while stirring at a rotation speed of 300 rpm using a two-blade stirring blade, an ultrasonic cleaner manufactured by SND Co., Ltd. (device name: US- The mixture was stirred while irradiating ultrasonic waves using 105). As a result, a test slurry (content of cerium hydroxide particles: 0.1% by mass) containing cerium hydroxide particles was prepared.

<Measurement of valence>
The test slurry was treated with a centrifuge (trade name: Optima MAX-TL) manufactured by Beckman Coulter Co., Ltd. at a centrifugal acceleration of 1.1 × 10 ⁴ G for 30 minutes to form a solid phase and a liquid phase (supernatant). ) Was separated. After removing the liquid phase, the solid phase was vacuum dried at 25 ° C. for 24 hours to obtain a measurement sample. The valence of cerium contained in the abrasive grains in this measurement sample was measured by X-ray photoelectron spectroscopy.

The trade name "K-Alpha" manufactured by Thermo Fisher Scientific was used as a measuring device for X-ray photoelectron spectroscopy (XPS). The measurement conditions are as follows.
[XPS conditions]
Path energy: 100 eV
Number of integrations: 10 times Binding energy: Range of 870 to 930 eV Excitation X-ray: monochromatic Al Kα 1, 2 lines (1486.6 eV)
X-ray diameter: 200 μm
Photoelectron escape angle: 45 °

Next, regarding the valence of cerium, the waveform caused by trivalent and the waveform caused by tetravalent were separated by using the analysis software attached to the apparatus. Waveform separation was performed according to the method described in the document "Surface Science vol.563 (2004) p.74-82". Then, the ratio of trivalents was calculated based on the following formula. The measurement results are shown in Table 1.
Percentage of trivalent = (Amount of trivalent [at%] / (Amount of trivalent [at%] + Amount of tetravalent [at%])

<Measurement of pH>
The pH of the test slurry was measured using model number PHL-40 manufactured by DKK-TOA CORPORATION. The measurement results are shown in Table 1.

<Measurement of zeta potential of abrasive grains>
An appropriate amount of test slurry was put into the trade name "DelsaNano C" manufactured by Beckman Coulter Co., Ltd. The measurement was performed twice at 25 ° C., and the average value of the displayed zeta potentials was adopted. The measurement results are shown in Table 1.

<Measurement of average grain size of abrasive grains>
An appropriate amount of each test slurry of Examples 1 to 4 and Comparative Example 1 was put into Microtrac MT3300EXII, a trade name manufactured by Microtrac Bell Co., Ltd., and the average particle size of the abrasive grains was measured. Further, an appropriate amount of the test slurry of Comparative Example 2 was put into the trade name: N5 manufactured by Beckman Coulter Co., Ltd., and the average particle size of the abrasive grains was measured. The displayed average particle size values were obtained as the average particle size (average secondary particle size) of the abrasive grains. The measurement results are shown in Table 1.

<Measurement of polishing speed>
The content of abrasive particles (total amount of particles) in the test slurry was adjusted to 0.1% by mass (diluted with ion-exchanged water) to obtain a CMP polishing liquid. The substrate to be polished was polished using this CMP polishing liquid under the following polishing conditions. The values of valence, pH, zeta potential of abrasive grains and average particle size in the CMP polishing liquid were equivalent to the values of the test slurry described above.
[CMP polishing conditions]
Polishing device: MIRRA (manufactured by Applied Materials)
Flow rate of CMP polishing liquid: 200 mL / min
Substrate to be polished: As a blanket wafer on which a pattern was not formed, a substrate to be polished having a silicon oxide film having a thickness of 2 μm formed by a plasma CVD method on a silicon substrate was used.
Polishing pad: Polyurethane foam resin with closed cells (Dow Chemical Japan Co., Ltd., model number IC1010)
Polishing pressure: 13 kPa (2.0 psi)
Rotation speed of substrate to be polished and polishing surface plate: substrate to be polished / polishing surface plate = 93/87 rpm
Polishing time: 1 min
Wafer cleaning: After the CMP treatment, the wafer was washed with water while applying ultrasonic waves, and further dried with a spin dryer.

_{The polishing rate (SiO 2} RR) of the silicon oxide film polished and washed under the above conditions was calculated from the following formula. The measurement results are shown in Table 1. The difference in film thickness of the silicon oxide film before and after polishing was determined using a light interference type film thickness measuring device (manufactured by Filmometrics Co., Ltd., trade name: F80).
Polishing speed (RR) = (difference in film thickness of silicon oxide film before and after polishing [nm]) / (polishing time: 1 [min])

Claims (8)

Containing abrasive grains and a liquid medium,
The abrasive grains include a first particle and a second particle in contact with the first particle.
The second particle contains at least one metal compound selected from the group consisting of metal oxides and metal hydroxides.
The metal compound contains a metal having a plurality of valences.
A slurry in which the ratio of the smallest valence among the plurality of valences of the metal is 0.10 or more in X-ray photoelectron spectroscopy. The slurry according to claim 1, wherein the smallest valence is trivalent. The slurry according to claim 1 or 2, wherein the metal contains a rare earth metal. The slurry according to any one of claims 1 to 3, wherein the metal contains cerium. Claims 1 to 1, wherein the first particle comprises at least one selected from the group consisting of silicon, vanadium, manganese, iron, cobalt, nickel, copper, silver, indium, tin, rare earth elements, tungsten, and bismuth. The slurry according to any one of 4. The slurry according to any one of claims 1 to 5, wherein the first particle contains a cerium oxide. The slurry according to any one of claims 1 to 6, wherein the zeta potential of the abrasive grains is +10 mV or more. A polishing method comprising a step of polishing a surface to be polished using the slurry according to any one of claims 1 to 7.